import java.util.*;
import java.math.*;

public class Fenzhi05{
	public static void main(String[] args) {
		Scanner reader = new Scanner(System.in);
		String x  = reader.nextLine();
		String[] xx = x.split(" ");
		int a = Integer.parseInt(xx[0]);
		int b = Integer.parseInt(xx[1]);
		int c = Integer.parseInt(xx[2]);
		//String x1 = aa[0];
		//String x2 = aa[1];
		//System.out.println(x1+" "+x2);
		if (a != b && a==c)
		{
			
			System.out.println("B");

		}
		else if(a != b && a != c)
		{
			System.out.println("A");
		}
		else
		{
			System.out.println("C");

		}

	}
}